A typical spatial light modulator in the art for use in display systems has an array of identical pixels. These pixels can be LED, OLED, LCD, Plasma, LCOS, micromirror, or other type of d pixels. In operation, the pixels are individually addressed and switched between operation states such as the ON and OFF state. In different states, incident light is directed in different directions, in the ON state producing desired illumination patterns on a display target (or for direct view).
As a way of example, a spatial light modulator may consist of an array of micromirror devices. Each micromirror device may have a deflectable reflective mirror plate formed on a substrate. An electrode is disposed at a location proximate to the mirror plate such that an electrostatic field can be established therebetween, and an electrostatic force derived from the electrostatic field can have sufficient strength to switch the mirror plate between the ON and OFF states. In the ON state, the mirror plate reflects the incident light onto a display target and produces a “bright” image pixel thereon. In the OFF state, the mirror plate reflects the incident light away from the display target and produces a “dark” pixel. By coordinating the reflective status of the micromirrors in the array, the micromirrors in the array collectively produce the desired image in the display target.
For a micromirror array of high uniformity, a monochromatic coherent light source, such as an arc lamp which is generally used in most current display systems may produce a diffraction pattern which conveys information regarding the underlying periodicity of the micromirror array. This undesired diffraction pattern overlaps with the displayed images, and can be perceived by viewers, resulting in an unpleasant visual effect.